Enhancers of cellular cannibalism for use to sensitize tumors to radiation therapy

ABSTRACT

The present invention is drawn to the use of the compounds highlighted in Tables 1 &amp; 2 and analogs thereof, for enhancing IR-mediated cellular cannibalism in cancer cells. Said compounds are herein called “enhancers of IR-mediated cellular cannibalism”. They can be used to enhance tumor immunogenicity and/or to induce a significant protective anticancer immune response in subjects that will receive or that have received a radiotherapy treatment. In other words, said compounds can be used to potentiate a radiotherapy treatment in a subject in need thereof. Said compounds are preferably chosen in the group consisting of: Mebhydroline 1,5-napthalene disulfonate salt, Flurbiprofen, Minaprine dihydrochloride, Myricetin, Digoxin, Digitoxin, Lanatoside, LOPA87, VP331, RN-1-026, SG6163F, VP450, and VP43.

SUMMARY

The present invention is drawn to the use of the compounds highlighted in Tables 1 & 2 and analogs thereof, for enhancing IR-mediated cellular cannibalism in cancer cells. Said compounds are herein called “enhancers of IR-mediated cellular cannibalism”. They can be used to enhance tumor immunogenicity and/or to induce a significant protective anticancer immune response in subjects that will receive or that have received a radiotherapy treatment. In other words, said compounds can be used to potentiate a radiotherapy treatment in a subject in need thereof. Said compounds are preferably chosen in the group consisting of: Mebhydroline 1,5-napthalene disulfonate salt, Flurbiprofen, Minaprine dihydrochloride, Myricetin, Digoxin, Digitoxin, Lanatoside, LOPA87, VP331, RN-1-026, SG6163F, VP450, and VP43.

BACKGROUND OF THE INVENTION

Radiotherapy is one of the most common anti-tumor strategies used in cancer treatments. More than half of patients with cancers are treated with radiotherapy. The use of radiotherapy (alone or in combination with surgery and chemotherapy) is central to the management of tumors of head and neck, breast, lung, prostate, digestive and cervical cancer¹. Exposure to ionizing radiation (IR) of tumor tissues triggers various lethal processes such as apoptosis, autophagic cell death, mitotic catastrophe or senescence.

These mechanisms contribute to the destruction of cancer cells in the irradiated tissues, but can also induce the immunogenicity of irradiated tumor cells^(2, 3), modify the tumor microenvironment and allow the development of an anti-tumor immune response involving the release of danger signals (adenosine triphosphate and HMGB1 protein)^(4, 5), the activation of purinergic receptors (notably P2X7 and P2Y2)⁴, the TLR4 receptor^(2, 3) and the NLRP3 inflammasome⁴. The relationship between the local tumor response and the stimulation of the immune system is illustrated by describing a remote effect on non-irradiated cancer cells. This paradoxical effect, also known as the abscopal effect, has been studied for many years in different murine tumor models as well as in patients⁶⁻⁹. Its detection correlates positively with the presence of a high amount of proinflammatory cytokines (such as TNF alpha), of interferon (IFN) gamma producing T cells and requires the development of an effective immunological response to be observed^(10, 11). This effect is also observed in patients treated with radiotherapy in combination with immuno-modulating agents (such as Ipilimumab or Interleukin-2)¹². The description of the abscopal effect reinforces the recent descriptions in many animal models of a major contribution of various components of the immune system to the response to radiotherapy. The central role of immune cells (including tumor-associated macrophages, T lymphoid cells and dendritic cells) has recently been studied and highlighted by the influence of their therapeutic modulation with modulators of immunological checkpoints (such as the use of monoclonal antibodies against CTLA4 or PD1) or macrophage activation (with monoclonal antibodies directed against CSF1R). Despite the central role of radiotherapy in the anti-tumor therapeutic arsenal, the biological processes involved in the elimination of tumor cells are still partially defined and controversial. Early studies on radio-induced tumor cell death are relatively old and occurred before the recent discovery of new cell death processes as well as of the central role of the immune system in the elimination of tumor cells following irradiation.

Scientific and technological advances in recent years revealed the existence of several processes of cell death. A classification of cell death modalities mainly built on morphological and functional criteria has been proposed¹³ and subdivided lethal processes into three distinct types: type I cell death (also known as apoptosis), type II cell death (or autophagy) and type III cell death (or necrosis). Initially organized on the apparent distinction between type I and III cell death modalities, between processes that are regulated or accidentally-induced, or by distinguishing cell deaths that are associated with the induction of by-stander inflammatory response in vivo, to lethal processes that were thinking silent or tolerogenic, this classification that still misnamed the type II cell death as autophagy (which is mainly an intracellular survival mechanisms required for the maintenance of cellular homeostasis) did not reflect the aptitude of necrotic deaths to be genetically controlled or immunogenic as revealed by the recent molecular characterization of necroptosis^(14, 15). In addition, cell death subroutines that did not or partially reveal these stereotyped morphological, metabolic and biochemical modifications (such as mitotic death and cornification) have been less studied and were grouped in a poorly defined subgroup of cell death modalities, also known as atypical cell death subgroup¹³.

In recent years, several new cell death mechanisms (such as entosis or emperitosis) have been described and associated to this neglected subgroup of cell death modalities^(16, 17). The characterization of these atypical death modalities highlighted the existence of cell death processes that are not achieved like typical cell death modalities, in a cell autonomous manner, but are elicited after the engulfment of lived cells by neighbor cells.

During decades, non-cell autonomous deaths (NCADs) have been episodically observed and studied. Initially referred as phagoptosis^(18, 19) or emperipolesis²⁰, these processes have been involved in the control of erythrocyte, neutrophil, platelet or T cell homeostasis^(18, 21, 22) and thus, proposed as major physiological forms of cell death in the body¹⁸. Detected as cell-in-cell structures, NCADs have been also observed during ex vivo culture of primary cells²³ or during histological analyses of physiological processes (such as embryo implantation²⁴ and intrahepatic depletion of autoreactive T cells²⁵) or human diseases (including cancer²³, inflammatory syndromes²³, during infectious diseases^(26, 27)). Mainly detected after homotypic interactions between malignant cells in human tumors (including breast, cervical and colon carcinomas or melanomas), NCADs are also detected after heterotypic interactions between tumor cells and stroma cells²⁸, tumor cells and immune effectors (such as lymphocytes²⁹ and NK cells³⁰), but may also be observed after interactions between immune effectors and epithelial cells (as revealed by the destruction of T cells in thymic nurse cells³¹ or autoreactive T cells in liver²⁵). Recently, NCAD was also associated with infectious diseases. The engulfment of Human immunodeficiency virus 1 (HIV-1) or Epstein barr virus (EBV) infected cells by uninfected cells has been detected during in vitro co-culture and the degradation of internalized infected cells proposed as the first step of a new cell-to-cell mode of viral transmission between infected cells and host cells^(26, 27), underlining the ability of NCADs to also contribute to microbial pathogenesis.

The first step of non-cell autonomous death programs starts with the interaction of two cellular partners through membrane adhesion receptors (such as E- or P-cadherins) or stress receptors (such as lipoprotein receptor-related protein) and is followed by the formation of adherent junctions between interacting cells that activates signaling pathways on both interacting cells and may involve small GTPases (such as Rho³² and Cdc42³³) and ROCK kinases¹⁶. Then, the modulation of actomyosin contractibility and the reorganization of the actin cytoskeleton on the level of “target” cells were shown to favor their invasion into host cells^(32, 34). This process is distinct from cellular cannibalism that can also trigger NCADs through the activation of specific signaling pathways (such as phagocytosis-related signaling pathways that involve cytoskeleton remodeling cell division cycle 42 (CDC42), chemokine (C—X—C motif) ligand 1 (CXCL1) or chemokine (C—X—C motif) ligand 6 (CXCL6)) on host cells and leads to an active engulfment of target cells³³. Once internalized, engulfed cells may be targeted by “host” lysosomal enzymes (such as cathepsins and granzymes) and eliminated through distinct lethal mechanisms that may involve several modulators of typical cell deaths (such as cytochrome c, caspases or autophagy-related (ATG) proteins). Entosis, a non-cell autonomous death, initially described after homotypic interactions between breast cancer cells, is cell-in-cell invasion mechanism that does not require the activation of caspases to eliminate engulfed cells¹⁶. Inversely the engulfment of natural killer (NK) by tumor cells initiates emperitosis, a progammed cell-in-cell death that requires caspase 3 activation and DNA fragmentation³⁰, revealing that engulfed cells can be eliminated through caspase-dependent or caspase independent processes.

Despite considerable efforts, the approaches developed over the last 10 years to enhance the effectiveness of radiotherapy have not met the expected clinical success. Among the reasons for the failures of the previous approaches, it can be pointed out that most of the approaches developed so far have characteristics different from those of the current project. Moreover, these approaches have not been developed using rational approaches based on the characterization of the mechanisms of cell death and resistance to therapy.

Specifically, they never took into account the impact of the immune system in the elimination of tumor cells. Finally, they merely transposed in radiotherapy applications coming from the field of medical oncology without taking into account specific mechanisms of cell death after irradiation.

In this context, there is a need to identify and characterize what are the modulators of cell death after radiotherapy irradiation and evaluate what are the immunological consequences of administering these modulators in cancer patients.

DESCRIPTION OF THE INVENTION

Despite the intensive biological and pharmaceutical research implemented to better characterize cellular and biochemical processes associated with anticancer treatments, lethal mechanisms responsible for the therapeutic effects of radiotherapy, which is one of the most frequent anticancer treatment used in clinic, are still unknown. Lethal processes (such as apoptosis and mitotic catastrophe) that have been detected in response to ionizing radiation were not directly implicated in treatment efficiency³⁵, suggesting that additional cell death modalities that are still unknown may contribute to therapeutic effects of radiotherapy.

The present project is based on the discovery of a new cell death mechanism (the cellular cannibalism) that has never been detected by others after RI or other anticancer treatments. Usually, in tumor vaccination experiments, cancer cells were exposed to cytotoxic anticancer treatment in vitro until 70% of the cells expose phosphatidylserine on the outer leaflet of the plasma membrane⁴⁸. Interestingly, the present results reveal that chemical compounds selected on the basis of their ability to enhance IR-mediated cellular cannibalism (IRCCE) convert cancer cells into a vaccine that stimulate antitumor immune responses. More specifically, the present results reveal for the first time that the combination of IRCCE+IR elicit an IR-mediated anticancer immune response in absence of a significant increase of death of treated and irradiated cells (FIG. 5A), suggesting that cellular cannibalism or cellular cannibalism-associated signaling pathways contributes to the induction of tumor immunogenicity after irradiation.

Irradiation is commonly used for treating cancer. Often combined with chemotherapy and/or surgery, irradiation therapy encompasses both local and total body administration as well as a number of new advances, including radio-immunotherapy. The cytotoxic effect of irradiation on neoplastic cells arises from the ability of irradiation to cause a break in one or both strands of the DNA molecule inside the cells. Cells in all phases of the cell cycle are susceptible to this effect. However, the DNA damage is more likely to be lethal in cancerous cells because they are less capable of repairing DNA damage. Healthy cells, with functioning cell cycle checkpoint proteins and repair enzymes are far more likely to be able to repair the radiation damage and function normally after treatment. Nevertheless, irradiation brings side effects that are a burden for the patients. The side effects of irradiation are similar to those of chemotherapy and arise for the same reason, i.e., the damage of healthy tissues. Irradiation is usually more localized than chemotherapy, but this treatment is still accompanied by damages to previously healthy tissue. Many of the side effects are unpleasant, and irradiation also shares with chemotherapy the disadvantage of being mutagenic, carcinogenic and teratogenic in its own right. While normal cells usually begin to recover from treatment within two hours of treatment, mutations may be induced in the genes of the healthy cells. These risks are elevated in certain tissues, such as those in the reproductive system. Also, it has been found that different people tolerate irradiation differently. Doses that may not lead to new cancers in one individual may in fact spawn additional cancers in another individual. This could be due to pre-existing mutations in cell cycle checkpoint proteins or repair enzymes, but current practice would not be able to predict at what dose a particular individual is at risk. Common side effects of irradiation include bladder irritation, fatigue, diarrhea, low blood counts, mouth irritation, taste alteration, loss of appetite, alopecia, skin irritation, change in pulmonary function, enteritis, sleep disorders, and others.

It would be highly advantageous to provide patients with a potentiating agent that triggers a synergistic effect with irradiation, thereby allowing the patient to be less exposed to irradiation therapy. This would indeed reduce the above-mentioned side-effects, while achieving an improved beneficial result. This is also an aspect of the present invention.

Altogether, it is proposed that, given the highlighted importance of cellular cannibalism on the elimination of irradiated cancer cells and the increasing importance of the immune response in tumor response to irradiation, cellular cannibalism is a “desirable” death that should be favored during cancer treatments in order to efficiently eliminate irradiated cancer cells. This can be achieved by administering to the patients cellular cannibalism enhancers as demonstrated by the present inventors in the experimental part below.

Definitions

The term “irradiation therapy” is commonly used in the art to refer to multiple types of radiation therapy including internal and external radiation therapy, radio-immunotherapy, and the use of various types of radiation including X-rays, gamma rays, alpha particles, beta particles, photons, electrons, neutrons, radioisotopes, and other forms of ionizing radiation. As used herein, the terms “irradiation therapy”, “radiation therapy”, “radiation” and “irradiation” are inclusive of all of these types of radiation therapy, unless otherwise specified. There are different types of radiotherapy machines, which work in slightly different ways. The number and duration of the radiotherapy sessions depend on the type of cancer and where it is located in the body. A superficial skin cancer may need only a few short treatments, whereas a cancer deeper in the body may need more prolonged treatment.

The terms “suppressing tumor growth”, “treating tumor growth”, and “treating cancer”, and the like refer to reducing the rate of growth of a tumor, halting tumor growth completely, causing a regression in the size of an existing tumor, eradicating an existing tumor and/or preventing the occurrence of additional tumors upon treatment with the compositions, kits or methods of the present disclosure. “Suppressing” tumor cell growth means any or all of the following states: slowing, delaying, and stopping tumor growth, as well as tumor shrinkage. “Delaying development” of a tumor means to defer, hinder, slow, retard, stabilize, and/or postpone development of the disease. This delay can be of varying lengths of time, depending on the history of the disease and/or individual being treated. Tumor cell growth can be assessed by any means known in the art, including, but not limited to, measuring tumor size, determining whether tumor cells are proliferating using a ³H-thymidine incorporation assay, or counting tumor cells.

As used herein, “synergy” or “synergistic effect” when referring to combination administration of a compound of the present disclosure in conjunction with radiation means that the effect of the combination is more than additive when compared to administration of the compound(s) and radiation alone.

“Potentiate” means, in the context of this application to enhance or increase the effect of, for example, a radiotherapy treatment, or to promote or strengthen, for example, a biochemical or physiological action or effect.

“Effective amount” refers to an amount of a compound as described herein that may be therapeutically effective to treat a cancer associated with the instant disclosure. The precise amount of these compounds required will vary with the particular compounds or derivatives employed, the age and condition of the subject to be treated, and the nature and severity of the condition. However, the effective amount may be determined by one of ordinary skill in the art with only routine experimentation. An effective amount of radiation can be determined without undue experimentation by one of ordinary skill in the art. Radiation parameters, such as dosing amount and frequency are well-known in the art.

“Pharmaceutically acceptable” refers to those compounds, materials, compositions, and/or dosage forms which are, within the scope of sound medical judgment, suitable for contact with the tissues of human beings and animals without excessive toxicity, irritation, allergic response, or other problem complications commensurate with a reasonable benefit/risk ratio.

“Pharmaceutically acceptable salts” refer to derivatives of the disclosed compounds wherein the parent compound is modified by making acid or base salts thereof. The compounds of this disclosure form acid and base addition salts with a wide variety of organic and inorganic acids and bases and includes the physiologically acceptable salts which are often used in pharmaceutical chemistry. Such salts are also part of this disclosure. Typical inorganic acids used to form such salts include hydrochloric, hydrobromic, hydroiodic, nitric, sulfuric, phosphoric, hypophosphoric and the like. Salts derived from organic acids, such as aliphatic mono and dicarboxylic acids, phenyl substituted alkonic acids, hydroxyalkanoic and hydroxyalkandioic acids, aromatic acids, aliphatic and aromatic sulfonic acids, may also be used. Such pharmaceutically acceptable salts thus include acetate, phenylacetate, trifluoroacetate, acrylate, ascorbate, benzoate, chlorobenzoatc, dinitrobenzoate, hydroxybenzoatc, mcthoxybenzoate, methyl benzoate, o-acetoxybenzoate, naphthalene-2-benzoate, bromide, isobutyrate, phenylbutyrate, β-hydroxybutyrate, butyne-1,4-dioate, hexyne-1,4-dioate, cabrate, caprylate, chloride, cinnamate, citrate, formate, fumarate, glycollate, heptanoate, hippurate, lactate, malatc, maleate, hydroxymaleate, malonate, mandelate, mesylate, nicotinate, isonicotinate, nitrate, oxalate, phthalate, teraphthalate, phosphate, monohydrogenphosphate, dihydrogenphosphate, metaphosphate, pyrophosphate, propiolate, propionate, phenylpropionate, salicylate, sebacate, succinate, suberate, sulfate, bisulfate, pyrosulfate, sulfite, bisulfite, sulfonate, benzene-sulfonate, p-bromobcnzenesulfonate, chlorobenzenesulfonate, ethanesulfonate, 2-hydroxyethanesulfonate, methanesulfonate, naphthalene-1-sulfonate, naphthalene-2-sulfonate, p-toleunesulfonate, xylenesulfonate, tartarale, and the like. Bases commonly used for formation of salts include ammonium hydroxide and alkali and alkaline earth metal hydroxides, carbonates, as well as aliphatic and primary, secondary and tertiary amines, aliphatic diamines. Bases especially useful in the preparation of addition salts include sodium hydroxide, potassium hydroxide, ammonium hydroxide, potassium carbonate, methylamine, diethylaminc, and ethylene diamine.

Alternative embodiments provide a method of potentiating radiotherapy cancer treatment as described, comprising the administration of a “slow-release formulation” that is able to release the active ingredient to the surroundings in a controlled, non-instant manner, time-dependent manner. This slow-release formulation may comprise a biodegradable polymer, for example selected from the group consisting of a homopolymer of lactic acid; a homopolymer of glycolic acid; a copolymer of poly-D,L,-lactic acid and glycolic acid; a water-insoluble peptide salt of a luteinizing hormone-releasing hormone (LHRH) analogue; a poly(phosphoester); a bis(p-carboxyphenoxy)propane (CPP) with sebacic acid copolymer; a polyanhydrides polymer; poly(lactide)-co-glycolide)polyethylene glycol copolymers; and an ethylene-vinyl acetate copolymer.

In some specific embodiments of the method, the slow-release formulation releases the IRCCE drug over a period of four or more weeks, alternatively over a period of one week or more, or alternatively over a period of few hours or more.

The methods, compositions formulations and uses described herein are suitable for both humans and animals, preferably mammals.

Thus, as used herein, the term “subject” relates to any mammal including a mouse, rat, pig, monkey and horse. In a specific embodiment, it refers to a human. A “subject in need thereof” or a “patient” in the context of the present invention is intended to include any subject that will benefit or that is likely to benefit from the methods and pharmaceutical compositions of the present invention. The subject may suffer from a cancer of any stage such that it could be an early non-invasive cancer or could be a late stage cancer that has already progressed to form metastases in the body.

“Patient” herein refers to animals, including mammals, preferably humans.

As used herein the term “cancer” is intended to include any form of cancer or tumors. Non-limiting examples of cancers include brain cancer (e.g., glioma), gastric cancer, head-and-neck cancer, pancreatic cancer, non-small cell lung cancer, small cell lung cancer, prostate cancer, colon cancer, non-Hodgkin's lymphoma, sarcoma, testicular cancer, acute non-lymphocytic leukemia and breast cancer. In a particular embodiment, the brain cancer is an astrocytoma, and more particularly, is glioblastoma multiforme; the lung cancer is either a small cell lung carcinoma or a non small cell lung carcinoma; and the head-and-neck cancer is squamous cell carcinoma or adenocarcinoma.

The present invention is based on the discovery that known and unknown drugs are able to enhance IR-mediated cellular cannibalism in vitro and in vivo in tumor-bearing animals.

As used herein, the terms “cellular cannibalism inducing drugs”, “cellular cannibalism inducing agents”, “cellular cannibalism inducing compounds” and “cellular cannibalism enhancers” designate compounds that are able to enhance the capacity of irradiation to trigger cellular cannibalism. Under these terms are designate compounds that are able to enhance IR-mediated cellular cannibalism (hereafter called IRCCE). The chemical structures of the selected cellular cannibalism modulators are presented in Table 1 and Table 2.

TABLE 1 Molecular weight Molecules Structures (g/mol) Myricetin

318.24 Minaprine dihydrochloride

371.3 Lanatoside C

985.12 Flurbiprofen

244.26 Mebhydroline 1,5- naphtalene- disulfonate

420.52 Azaguanine-8

152.11 Digitoxigenin

390.51 Doxorubicin hydrochloride

579.98 Digoxin

780.949

TABLE 2 Molecular Molecules Structures weight (g/mol) RN-1-001

320 VP43

425 VP450

287 SG6163F

348 RN-1-026

346 VP331

350 LOPA87

291

In total, the present inventors discovered 16 efficient cellular cannibalism enhancer compounds, namely: 8-Azaguanine, Mebhydroline 1,5-napthalene disulfonate salt, Flurbiprofen, Minaprine dihydrochloride, Myricetin, Digoxin, Digitoxin, Lanatoside, Doxorubicine hydrochloride, LOPA87, VP331, RN-1-026, SG6163F, VP450, VP43. A number of interesting compounds have been also identified. They are for examples analogs of LOPA87 (LOPA90, LOPA93, LOPA 94, LOPA 101, LOPA104, LOPA105, LOPA106) and analogs of SG6143F (SG6144, SG6146 and SG6149). Therefore, in a preferred embodiment, the cellular cannibalism enhancers of the invention are chosen in the group consisting of: 8-Azaguanine, Mebhydroline 1,5-napthalene disulfonate salt, Flurbiprofen, Minaprine dihydrochloride, Myricetin, Digoxin, Digitoxin, Lanatoside, Doxorubicine hydrochloride, LOPA87, VP331, RN-1-026, SG6163F, VP450, and VP43, the structures of which are displayed in Tables 1 and 2. In a more preferred embodiment, the cellular cannibalism enhancers of the invention are chosen in the group consisting of: Mebhydroline 1,5-napthalene disulfonate salt, Flurbiprofen, Minaprine dihydrochloride, Myricetin, Digoxin, Digitoxin, Lanatoside, LOPA87, VP331, RN-1-026, SG6163F, VP450, and VP43. In an even more preferred embodiment, the cellular cannibalism enhancers of the invention are chosen in the group consisting of: 8-Azaguanine, Minaprine dihydrochloride, LOPA87, VP331, and SG6163F.

They can also be analogs of LOPA87, such as LOPA90, LOPA93, LOPA 94, LOPA 101, LOPA104, LOPA105, and LOPA106.

They can also be analogs of SG6163F, such as SG6144, SG6146 and SG6149.

8-Azaguanine (C₄H₄N₆O, Purine analogue). The 8-Azaguanine is a purine analogue with potential antineoplastic activity. 8-Azaguanine interferes with the modification of transfer ribonucleic acid (tRNA) by competing with guanine for incorporation into tRNA catalyzed by the enzyme tRNA-guanine ribosyltransferase (tRNA-guanine transglycosylase). Altered guanine modification of tRNA has been implicated in cellular differentiation and neoplastic transformation. 8-Azaguanine also inhibits the formation of 43S and 80S initiation complexes, thereby interfering with initiation of translation and inhibiting protein synthesis. This agent inhibits tumor cell growth and stimulates cell differentiation.

Mebhydroline 1,5-naphtalene disulfonate salt (C₁₉H₂₀N₂._(1/2)C₁₀H₈O₆S₂, a H1 histamine receptor antagonist). The Mebhydrolin (napadisylate) is an antihistamine, used for symptomatic relief of allergic symptoms caused by histamine release, including nasal allergies and allergic dermatosis.

Flurbiprofen (C₁₅H₁₃FO₂, phenylalkanoic acid derivative family of non-steroidal anti-inflammatory drugs (NSAIDs)). Flurbiprofen is used to relieve pain, tenderness, swelling, and stiffness caused by osteoarthritis (arthritis caused by a breakdown of the lining of the joints) and rheumatoid arthritis (arthritis caused by swelling of the lining of the joints). Flurbiprofen is in a class of medications called NSAIAs (nonsteroidal anti-inflammatory agents). It works by stopping the body's production of a substance that causes pain, fever, and inflammation. This nonsteroidal anti-inflammatory agent of the propionic acid class is structurally and pharmacologically related to fenoprofen, ibuprofen, and ketoprofen, and has similar pharmacological actions to other prototypica NSAIAs. Flurbiprofen exhibits anti-inflammatory, analgesic, and antipyretic activities. The commercially available flurbiprofen is a racemic mixture of (+) S- and (−) R-enantiomers. The S-enantiomer appears to possess most of the anti-inflammatory, while both enantiomers may possess analgesic activity. Similarly to other NSAIAs, the anti-inflammatory effect of flurbiprofen occurs via reversible inhibition of cyclooxygenase (COX), the enzyme responsible for the conversion of arachidonic acid to prostaglandin G2 (PGG2) and PGG2 to prostaglandin H2 (PGH2) in the prostaglandin synthesis pathway. This effectively decreases the concentration of prostaglandins involved in inflammation, pain, swelling and fever. Flurbiprofen is a non-selective COX inhibitor and inhibits the activity of both COX-1 and -2. It is also one of the most potent NSAIAs in terms of prostaglandin inhibitory activity.

Minaprine dihydrochloride (C₁₇H₂₂N₄O, amino-phenylpyridazine antidepressant). Minaprine dihydrochloride is a psychotropic drug which has proved to be effective in the treatment of various depressive states. Like most antidepressants minaprine antagonizes behavioral despair. Minaprine is an amino-phenylpyridazine antidepressant reported to be relatively free of cardiotoxicity, drowsiness, and weight gain. More specifically, minaprine is an amino-phenylpyridazine antidepressant reported to be relatively free of cardiotoxicity, drowsiness, and weight gain. Similar to other antidepressant treatments, minaprine attenuates the beta-adrenergic receptor function. Studies have also shown that minaprine improves memory consolidation and that repeated drug administration leads to potentiation of this effect. Moreover, the effects of minaprine on memory consolidation are related to its dopaminergic action. Minaprine binds to serotonin type 2 receptors and to dopamine D1 and D2 type receptors. It also binds to the serotonin reuptake pump. Therefore, minaprine blocks the reuptake of both dopamine and serotonin. It is also, to a slight degree, cholinomimetic. Thus it may exhibit both mood-brightening and nootropic properties. It also acts as a reversible inhibitor of MAO-A (RIMA). It has also been found to inhibit acetylcholinesterase.

Myricetin (C₁₅H₁₀O₈, benzopyrans, small molecule). The Phosphatidylinositol 4,5-bisphosphate 3-kinase catalytic subunit gamma isoform has been proposed as cellular target.

Digoxin (C₄₁H₆₄O₁₄, Cardiac glycoside). Digoxin, a cardiac glycoside similar to digitoxin, is used to treat congestive heart failure and supraventricular arrhythmias due to reentry mechanisms, and to control ventricular rate in the treatment of chronic atrial fibrillation.

Digitoxin (C₄₁H₆₄O₁₃, Cardiac glycoside). Digitoxin is a lipid soluble cardiac glycoside that inhibits the plasma membrane sodium potassium ATPase, leading to increased intracellular sodium and calcium levels and decreased intracellular potassium levels. In studies increased intracellular calcium precedes cell death and decreased intracellular potassium increase caspase activation and DNA fragmentation, causing apoptosis and inhibition of cancer cell growth.

Lanatoside C (C₄₉H₇₆O₂₀, Cardiac glycoside). Lanatoside C, isolated from various species of digitalis, is used in the treatment of congestive heart failure and cardiac arrhythmia.

Doxorubicine hydrochloride (C₂₇H₂₉NO₁₁, Cancer chemotherapy). Doxorubicin Hydrochloride is the hydrochloride salt of doxorubicin, an anthracycline antibiotic with antineoplastic activity. Doxorubicin, isolated from the bacterium Streptomyces peucetius var. caesius, is the hydroxylated congener of daunorubicin. Doxorubicin intercalates between base pairs in the DNA helix, thereby preventing DNA replication and ultimately inhibiting protein synthesis. Additionally, doxorubicin inhibits topoisomerase II which results in an increased and stabilized cleavable enzyme-DNA linked complex during DNA replication and subsequently prevents the ligation of the nucleotide strand after double-strand breakage. Doxorubicin also forms oxygen free radicals resulting in cytotoxicity secondary to lipid peroxidation of cell membrane lipids; the formation of oxygen free radicals also contributes to the toxicity of the anthracycline antibiotics, namely the cardiac and cutaneous vascular effects.

Chemical Compounds Obtained from the Screened Library

LOPA87, VP331, RN-1026, SG6163F, VP450 and VP43 have been obtained from the CEA library. 7 analogs of LOPA87 (LOPA90, LOPA93, LOPA 94, LOPA 101, LOPA104, LOPA105, LOPA106) and 3 analogs of SG6163F (SG6144, SG6146 and SG6149) were also identified.

Aspects of the Invention

In a first aspect, the present invention is drawn to the in vitro use of the above-identified compounds (highlighted in Tables 1 & 2) for enhancing IR-mediated cellular cannibalism (IRCCE) of cancer cells.

This aspect of the invention is performed in vitro. As disclosed herein, the terms “in vitro” and “ex vivo” are equivalent and refer to studies or experiments that are conducted using biological components (e.g. cells or population of cells) that have been isolated from their usual host organisms (e.g. animals or humans). Such isolated cells can be further purified, cultured or directly analyzed to assess the presence of the mutant proteins. These experiments can be for example reduced to practice in laboratory materials such as tubes, flasks, wells, eppendorfs, etc. In contrast, the term “in vivo” refers to studies that are conducted on whole living organisms.

IR-mediated cellular cannibalism can be assessed by any conventional means. In particular, this activity can be assessed by studying the cells under the microscope (by immunofluorescence or immunohistochemistry) and by visually detecting cell engulfment events or cell-in-cell systems. Alternatively, it can be assessed by measuring, in said cell, the expression level of a protein selected from the group consisting of: p53, p53β, p53γ, and N-terminal isoforms of p53 that lack the N-terminal transactivating domain, such as Δ40TP53 and Δ133TP53, or by measuring the expression level or the activity of the purinergic P2Y2 receptor, and/or by measuring the extracellular ATP secreted by said cells, as disclosed in WO2014/006227 which is incorporated herein by reference.

The compounds of the invention can also be used in vivo.

In this case, the compounds of the invention are preferably administered to the patients in a pharmaceutical composition further containing pharmaceutically acceptable adjuvants. The “pharmaceutical composition of the invention” therefore contains an efficient amount of at least one of the compound of the invention (see Table 1 & 2 above), or analogs thereof, and pharmaceutically acceptable adjuvants or carriers. Examples of non-aqueous adjuvants are propylene glycol, polyethylene glycol, vegetable oil and injectable organic esters such as ethyloleate. Other pharmaceutically acceptable adjuvants include aqueous solutions and non-toxic excipients including salts, preservatives, buffers and the like. Intravenous vehicles include fluid and nutrient replenishers. The compositions may also include preservatives such as antimicrobial agents, anti-oxidants, chelating agents and inert gases. The pH and exact concentration of the various components of the pharmaceutical composition can be adjusted according to well-known parameters.

The in vivo administration of the compounds of the invention (or of the composition of the invention) is intended to enhance the tumor immunogenicity in subjects that will or that have undergone a radiotherapy treatment. While not being bound to any particular theory, it is believed that these compounds work synergistically with radiation therapy by favoring cellular cannibalism and thereby the exposure of particular epitopes that induce a significant protective anticancer immune response.

The present disclosure targets the use of the compounds disclosed in Tables 1 & 2 above or their analogs for manufacturing a pharmaceutical composition intended to be administered prior or after radiotherapy to a subject in need thereof.

It is also drawn to the use of the compounds disclosed in Tables 1 & 2 above or their analogs for manufacturing a pharmaceutical composition intended to potentiate a radiotherapy treatment to a subject in need thereof.

It is finally drawn to the use of the compounds disclosed in Tables 1 & 2 above or their analogs for manufacturing a pharmaceutical composition intended to treat cancer, in conjunction with radiotherapy, in a subject in need thereof.

In a second aspect, the present invention is drawn to the compounds disclosed in Tables 1 & 2 above or their analogs, or any pharmaceutical composition containing same,

-   -   for their use for enhancing IR-mediated cellular cannibalism in         patients suffering from cancer,     -   for their use for enhancing tumor immunogenicity in subjects         that will or that have received a radiotherapy treatment,     -   for their use for inducing a significant protective anticancer         immune response in subjects that will or that have received a         radiotherapy treatment,     -   for their use for potentiating a radiotherapy treatment in a         subject in need thereof,     -   for their use for treating cancer, in conjunction with         radiotherapy, in a subject in need thereof.

Importantly, administering the compositions of the invention will enable to reduce the dose of irradiation and therefore results in the alleviation of the side effects incurred by the radiation treatment.

The pharmaceutical compositions of the present invention can be administered in the form of injectable compositions (e.g., intravenously, intramuscularly, subcutaneously and intra-articularly), either as liquid solutions or suspensions; solid forms suitable for solution in, or suspension in, liquid prior to injection also may be prepared. These preparations also may be emulsified.

Said pharmaceutical compositions can also be administered by other routes such as orally, nasally, rectally, topically, intravenously, intramuscularly, subcutaneously, sublingually, intrathecally, intraperitoneally, intra-articularly or intradermally. Preferably, the route of administration is intravenously, intra-arterially or orally. Preferably, the pharmaceutical compositions are administered intravenously or intra-arterially.

In specific embodiments, when the composition of the present invention is for oral administration, the composition of the invention is in a tablet, a solution or capsule such as a soft gel capsule for example. In other specific embodiments, when the composition of the present invention is for oral administration, it has an enteric coating. In other specific embodiments, when the composition of the present invention is for oral administration, it is an oil-based syrup.

In a particular embodiment, the compounds of the invention are administered in a slow-release formulation.

The compositions of the present invention are administered in amounts and at frequencies sufficient to treat cancer, in conjunction with a radiotherapy treatment. A subject's progress can be determined by measuring and observing changes in the concentration of cancer markers; by measuring the actual size of the tumor over time and/or by determining any other relevant clinical markers which are well-known in the art. The determination, measurement, and evaluation of such characteristics and markers associated with clinical progress are well-known to those of ordinary skill in the art.

In an embodiment, the compositions of the present invention are administered prior to radiotherapy. The time of administration will depend on the specific formulation and on the time necessary for the cellular cannibalism enhancer to reach the target cells. The time of administration will be chosen so as to provide the optimal concentration of cellular cannibalism enhancer at the time of irradiation.

In another embodiment, the compositions of the present invention are administered after the radiotherapy treatment has been applied to the patient.

In another embodiment, the administration of the compositions of the present invention and the radiotherapy treatment has been applied concomitantly to the patient

The present inventors observed that the administration of minaprine dihydrochloride alone has intrinsic protective effects against tumor development (see FIGS. 6B, 6G, 6L, 6P and 6Q). Consequently, minaprine dihydrochloride does not need to be combined with a radiotherapy treatment, it is efficient on its own. This is a surprising result, since minaprine dihydrochloride is known as an anti-depressant drug, and no anti-tumoral effect has ever been reported for this drug.

In a third aspect, the present invention therefore addresses minaprine dihydrochloride, or any pharmaceutical composition containing same,

-   -   for its use for treating patients suffering from cancer,     -   for its use for inducing a significant protective anticancer         immune response in cancer patients.     -   For its use for treating cancer when combined with a         radiotherapy or chemotherapy or immunotherapy treatment.

All the embodiments disclosed above for the pharmaceutical compositions are transposable to this particular use.

Methods of Treatment

The present disclosure also provides methods aiming at enhancing IR-mediated cellular cannibalism (IRCCE) in patients suffering from cancer, enhancing tumor immunogenicity in subjects that will or that have received a radiotherapy treatment, inducing a significant protective anticancer immune response in subjects that will or that have received a radiotherapy treatment, potentiating a radiotherapy treatment in a subject in need thereof, and/or treating cancer, in conjunction with radiotherapy, in a subject in need thereof.

In these methods, the compounds of the invention (see Table 1, Table 2, and analogs thereof as detailed above) or the pharmaceutical compositions of the invention (as disclosed above) are administered to said subject prior to, or after or concomitantly the treatment with radiotherapy.

The present invention also targets a method for treating cancer patients, comprising administering to said patients an effective amount of minaprine dihydrochloride, or any pharmaceutical composition containing same, As a matter of fact, said anti-depressant drug has been shown by the inventors to have a significant protective anticancer immune response on its own.

Screening Methods

In another embodiment, the present invention relates to an in vitro method of identifying a compound that may potentiate a radiotherapy treatment in a subject, said method comprising the steps of:

(a) adding a candidate compound to a tumor cell culture,

(b) treating said tumor cell culture with a radiation dose of 1-20 Gray,

(c) measuring the irradiation-mediated cellular cannibalism occurring in said cell culture,

wherein a compound that enhances irradiation-mediated cellular cannibalism as compared to control levels will be able to potentiate a radiotherapy treatment.

As mentioned above, IR-mediated cellular cannibalism can be assessed by any conventional means. In particular, this activity can be assessed by studying the cells under the microscope (by immunofluorescence or immunohistochemistry) and by visually detecting cell engulfment events or cell-in-cell systems. Alternatively, it can be assessed by measuring, in said cell, the expression level of a protein selected from the group consisting of: p53, p53β, p53γ, and N-terminal isoforms of p53 that lack the N-terminal transactivating domain, such as Δ40TP53 and Δ133TP53, or by measuring the expression level or the activity of the purinergic P2Y2 receptor, and/or by measuring the extracellular ATP secreted by said cells, as disclosed in WO2014/006227 which is incorporated herein by reference.

Alternatively, the treatment of the cell culture with irradiation can be performed prior to the adding of the candidate compound to the cell culture.

In a preferred embodiment, the radiation dose used in step b) is comprised between 1-10Gray, typically at 8Gray.

In a preferred embodiment, the tumor cell culture is treated with the candidate compound for at least 12 hours, more preferably for at least 20 hours, even more preferably for 24 hours, prior or after the irradiation occurs.

Said tumor cell culture can be a culture of HCT116 cells, of CT26 carcinoma cells, of MCA205 fibrosarcoma cells.

The confirmation of the potentiating effect of the candidate compound can be performed as described in the examples below, i.e., by treating the appropriate tumor cell cultures with the compounds for at least 12 hours, and applying an irradiation treatment, and then inject these cells into immunocompetent mice, in order to confirm that a protective immune response has been elicited.

According to the experimental part below, the compounds disclosed in Tables 1 & 2 above and their analogs are herein designated as examples of “enhancers of IR-mediated cellular cannibalism”.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 Cell Death Profiling by quantitative imaging flow-cytometry. (A) Principle of cell death profiling by quantitative flow imaging. (B) Validation of multiparametric and simultaneous detection of cell death modalities by quantitative imaging flow-cytometry induced by gamma-irradiation. Before co-culture, treated HCT116 cells and non-treated HCT116 cells were respectively labeled with CMFDA (green/light grey) or CMTMR (red/dark grey) fluorescent vital probes. After 24 hours of co-culture, HCT116 cells were analysed for non-cell autonomous death (NCAD) (by detecting engulfment of CMTMR- or CMFDA-labeled HCT116 cells), for phosphatidylserine (PS) exposure (using Biotin-AnnexinV and BV786-Streptavidin), for loss of plasma integrity (by following with DRAQ7 uptake) and for DNA content (using Hoechst 33342). Using quantitative flow-cytmotery, the simultaneous detection of NCA deaths and of typical cell deaths (Type I, II and III) on both non-treated and treated HCT116 cells will determine the cell death profiling obtained after cancer treatment. Representative images are shown (scale, 20 μm).

FIG. 2 Detection of γ-irradiation-elicited cell autonomous death modalities by quantitative imaging flow-cytometry. (A-E) Detection and quantification of plasma membrane integrity loss and PS exposure observed after 24 hour co-culture of untreated (red/dark grey) CMTMR-labeled HCT116 cells and untreated (green/light grey) CMFDA-labeled HCT116 cells (A, C-E), of untreated (red/dark grey) CMTMR-labeled HCT116 cells and untreated (green/light grey) CMFDA-labeled HCT116 cells that have been extemporally mixed (C-E) or after 24 hour co-culture of untreated (red/dark grey) CMTM-labeled HCT116 cells with (green/light grey) CMFDA-labeled HCT116 cells (green) that have been irradiated with 4 grays of γ-ionizing radiation (B-E). The co-cultures have been performed in presence or absence of the indicated pharmacological death effector inhibitors. The detection of plasma membrane integrity (with DRAQ7) and PS exposure (with BV786-streptavidin/Annexin V biotin) have been analyzed for the untreated (red/dark grey) CMTMR⁺ HCT116 cells, for untreated (green/light grey) CMFDA⁺ HCT116 cells, for treated (green/light grey) CMFDA⁺ HCT116 cells and for total cell population (CMTMR⁺ or CMFDA⁺ HCT116 cells). Representative dot plots (A,B) and quantitative data (C-E) are shown (means±SEM, n=3). (F,G) Representative cell cycle distributions of untreated (red/dark grey) CMTMR⁺ HCT116 cells, untreated (green/light grey) CMFDA⁺ HCT116 cells, treated (green/light grey) CMFDA⁺ HCT116 cells and for total cell population (CMTMR⁺ or CMFDA⁺ HCT116 cells) obtained after 24 hour co-culture of untreated (red/dark grey) CMTMR-labeled HCT116 cells with untreated (green/light grey) CMFDA-labeled HCT116 cells (F, H-J), of untreated (red/dark grey) CMTMR-labeled HCT116 cells and untreated (green/light grey) CMFDA-labeled HCT116 cells that have been extemporally mixed (H-J) or after 24 hour co-culture of untreated (red/dark grey) CMTM-labeled HCT116 cells with (green/light grey) CMFDA-labeled HCT116 cells (green/light grey) that have been irradiated with 4 grays of γ-ionizing radiation (G-J) are shown. Quantitative data of cell cycle analysis are shown in (H-J) (means±SEM, n=3). * or # or $ represents p<0.05, ## or $$ p<0.01, *** or ### p<0.001.

FIG. 3 Detection of γ-irradiation-elicited non-cell autonomous death modalities by quantitative imaging flow-cytometry and confocal fluorescence microscopy. (A-G) Cell-in-cell structures and target cell degradation were determined by quantitative imaging (A-C) and confocal fluorescent microscopy (D-G) after 24 hour co-culture of untreated (red/dark grey) CMTM-labeled HCT116 cells with (green/light grey) CMFDA-labeled HCT116 cells that have been irradiated with 4 grays of γ-ionizing radiation (A), coculture of untreated (red/dark grey) CMTMR-labeled HCT116 cells with untreated (green/light grey) CMFDA-labeled HCT116 cells (B, C) or on CMTMR labeled (red/dark grey) HCT116 cells and untreated (green/light grey) CMFDA-labeled HCT116 cells that have been extemporally mixed (B, C). As previously described, cells have been sequentially labeled after co-cultures with specific fluorescent probes like BV786-streptavidin-Annexin V biotin, DRAQ7, and Hoechst 33342. Then, (red/dark grey) CMTMR-labeled HCT116 cells internalizing (green/light grey) CMFDA-labeled HCT116 cells (noted R(G)), and (green/light grey) CMFDA-labeled HCT116 cells internalizing (red/dark grey) CMTMR-labeled HCT116 cells (noted G(R)) were detected. Representative images are shown in (A) (scale, 20 m). Frequencies of Cell-in-Cell structures (B) and target cell degradation (C) are reported (means±SEM, n=3). Representative confocal images of cell-in-cell structures (white arrow) (D) and target cell degradation (white dotted arrow) (E) detected during co-culture of untreated (red) CMTMR-labeled HCT116 cells with untreated or γ-irradiated (green) CMFDA-labeled cells are shown (scale bar=10 m). (F-G) Frequencies of cell-in-cell structures showing (red/dark grey) CMTMR-labeled cells internalizing (green/light grey) CMFDA-labeled cells (noted R(G)), and (green/light grey) CMFDA-labeled cells internalizing (red/dark grey) CMTMR-labeled cells (noted G(R)) (F) and target cell degradation (G) have been determined (means±SEM, n=3); # or $ represents p<0.05, ## or $$ p<0.01, *** or $$$ or ### p<0.001.

FIG. 4 Identification of cannibalism modulators triggered by ionizing radiation. Compounds from the Prestwick (A) and CEA (F) libraries were tested for their capacities to induce cellular cannibalism after ionizing radiation. Cannibal cells were detected after homotypic cultures of 8 gray γ-irradiation HCT116 cells in the presence or absence of μM of the Prestwick (A) and CEA (E) library compounds. Each dot represents one compound. Representative images are shown in (B, G). (C, H) HCT116 cells were treated with the indicated drugs. After 24 h of treatment, cell death was monitored by staining with 3,3 dihexyloxacarbocyanine iodide (DiOC₆(3)) and PI, and the percentage of dying (DiOC₆(3)^(low) PI⁻, open bars) and dead (DiOC₆(3)^(low) PI⁺, closed bars) cells was determined by cytofluorometry. Validation of the cannibalism inducers by fluorescent microscopy. Representative images (D, I) and quantification (E, J) are shown. Results are means±s.e.m. of triplicate determinations.

FIG. 5. Identification of cannibalism modulators as immunogenic cell death inducers. MCA205 (A) or CT26 (E, I, M, Q) cells were treated with the indicated drugs. After 24 h of coculture with the indicated treatment, cell death was monitored by staining DiOC₆(3) and PI, and the percentage of dying (DiOC₆(3)^(low) PI⁻, open bars) and dead (DiOC₆(3)^(low) PI⁺, closed bars) cells was determined by cytofluorometry. (B-D) MCA205 cells or (F-H, J-L, N-P, R-T) CT26 cells cocultured after x irradiation with the indicated compounds were inoculated subcutaneously into the right flank of C56BL/6 or BALB/c mice, respectively. Seven days later, the mice were rechallenged with live cells injected into the opposite flank, and tumor growth was monitored (five mice per group).

FIG. 6. Tumor vaccination experiments. CT26 cells were treated for 24 hours with 10 μM VP331 (A, F, K), 10 μM Minaprine (B, G, L), 10 μM Lopa87 (C, H, M), 10 μM SG6163F (D, I, N), 10 μM Azaguanine-8 (8-aza) (E, J, O) alone or combined with 8 Gy ionizing radiation and inoculated (s.c.) into immunocompetent BALB/c mice, which were rechallenged at the opposite flank 7 days later with the same cancer cells. The percentage of tumor-free mice was evaluated three times a week for the following 38 days. Percentage of total tumor free mice (A-E), tumor free-mice at the first injection site (F to J, P) or at the second injection site (K to O, Q) are shown. (*P<0.05, **P<0.01, ***P<0.001, two-way ANOVA).

EXAMPLES

I. Material and Methods

Chemicals, Cell Lines and Culture Conditions

Unless otherwise indicated, chemicals were purchased from Sigma-Aldrich. Antibiotics, media, supplements for cell culture were obtained from Life Technologies. Benzyloxycarbonyl-Val-Ala-Asp(OMe)-fluoromethylketone (Z-VAD-fmk) was from Bachem and recombinant mouse TNF-alpha from R&D systems. Human colon carcinoma HCT116 cells were cultured in McCoy's 5A medium and murine fibrosarcoma cell line L929 in Dulbecco's modified Eagle's medium. All the media were supplemented with 10% heat-inactivated fetal bovine serum (FBS), 10 mM HEPES buffers, 2 mM L-glutamine, 10 U/mL penicillin sodium and 10 μg/mL streptomycin sulfate.

Irradiation

Cells were seeded in 6-well plates, 12-well plates or 25 cm² flasks and irradiated at indicated dose with gamma-ray irradiator IBL-637 (Cs¹³⁷, 1 Gy/min, gamma CIS-Biolnternational, IBA, Saclay, France).

CellTracker™ Fluorescent Probes Labeling

Upon the removal of the culture medium, HCT116 cells were incubated with pre-warmed medium containing 10 μM of 5-chloromethylfluorescein diacetate (CMFDA, green fluorescence) or 5-(and-6)-(((4-Chloromethyl)Benzoyl)Amino)Tetramethylrhodamine (CMTMR, red fluorescence) (Molecular Probes-Life Technologie) for 45 min at 37° C. Thereafter, HCT116 cells were rinsed twice with pre-warmed medium, and incubated for 1 hour at 37° C. Stained cells were treated as indicated and cultured for cell death profiling analysis.

Cell Death Profiling by Quantitative Flow Imaging

Untreated HCT116 cells were labeled with CMFDA (green fluorescence, CMFDA⁺) or CMTMR, (red fluorescence, CMTMR⁺) and treated HCT116 cells with CMFDA (green fluorescence, CMFDA⁺). The following cell mixtures were performed: untreated CMTMR⁺ HCT116 cells were mixed with untreated CMFDA⁺ HCT116 cells, or untreated CMTMR⁺ HCT116 cells were mixed with treated CMFDA⁺ HCT116 cells. Then, cells were co-cultured during 24 hours in the presence or absence of the pharmacological inhibitor of ROCK, Y27632 (30 μM), the pan-caspase inhibitor, Z-VAD-fmk (ZVAD, 100 μM), the inhibitor of caspase-1, Ac-YVAD-cmk (YVAD, 100 μM), the necroptosis inhibitor, Necrostatin-1 (NEC 1, 30 μM), the inhibitor of the vacuolar type H(+)-ATPase (V-ATPase) inhibiting autophagy, Bafilomycin A1 (BafA1, 50 nM), the inhibitor of Cdks with an anti-mitotic activity, Roscovitine (Rosco, 10 μM). After 24 hours of co-culture, both detached and adherent cells were collected and stained with Hoechst 33345 (10 g/mL) during 1 hour at 37° C. in warmed complete medium. To detect phosphatidylserine (PS) exposure and plasma membrane permeability, labeled HCT116 cells were successively incubated with Biotin-AnnexinV (BD Pharmingen) as recommended by manufacturer, 0.5 g BV786-Streptavidin (BD Biosciences) and 3 M DRAQ7 (BioStatus) during 15 minutes at 25° C. After washing with PBS solution, samples were immediately analyzed using an imaging flow cytometer FlowSight® (Amnis®, part of EMD Millipore). Data were acquired at a 20× magnification, using INSPIRE software. The 405 nm, 488 nm, and 561 nm lasers were used for excitation. Brightfield, Annexin V-BV786, DRAQ7, CMFDA, CMTMR and Hoechst 33345 stainings were detected using respectively channels for 420-480 nm, 745-800 nm, 642-745 nm, 480-560 nm, 595-642 nm and 430-505 nm. At least 1000 events of cells per sample were analyzed. Additional single-labeled controls were prepared to normalize fluorescent signal across different channels. Acquired data were analyzed using the IDEAS analysis software (v6.1; Merck-Millipore). Gating strategy was the following. Cells were gated for focused cells using the Gradient RMS feature. Cells were gated for single cells using the aspect ratio and area features. For the cannibalism detection, cells were gated in the double positive CMFDA⁺ and CMTMR⁺ staining.

Flow Cytometry and Confocal Fluorescent Microscopy

To detect PS exposure, plasma membrane permeability and cell cycle progression, cells were after co-culture sequentially labeled with specific fluorescent probes (such as FITC-conjugated AnnexinV, propidium iodide, and Hoechst 33342) and analyzed by flow cytometry. Both detached and adherent cells were collected and stained with Hoechst 33345 (10 ug/ml) during 1 hour at 37° C. in warmed complete medium. After washing with PBS, HCT116 cells were suspended in 1X binding buffer supplemented with fluorescein isothiocyanate (FITC)-conjugated Annexin V (BD Biosciences) and propidium iodide (PI, 1 μg/mL) (Sigma), as per manufacturer's instructions. Samples were then analyzed using LSRII flow cytometer (Becton Dickinson) and the FlowJo software v10. For confocal fluorescence microscopy, HCT116 cells were fixed after co-culture in 3,7% paraformaldehyde-PBS for 15 minutes and counterstained with 1 μg/mL Hoechst 33342 (Invitrogen) for 15 minutes. Then, cells were analyzed by confocal SPE microscope equipped with Apochromat 63×1.3 NA and 63×1.15 NA oil immersion objectives. The Leica Application Suite (LAS) software was used (Leica Microsystems).

Western Blots

Total cellular proteins were extracted in lysis buffer (containing 1% NP40, 20 mmol/L HEPES, 10 mmol/L KCl, 1 mmol/L EDTA, 10% glycerol, protease and phosphatase inhibitor tablets). Protein extracts (30 μg) were run on 4-12% NuPAGE® Novex® Bis-Tris gels (Life Technologies) and transferred at 4° C. onto Immobilon polyvinyldifluoride (PVDF) membranes (Thermo Scientific). After blocking, membranes were incubated at 4° C. overnight with primary antibodies specific for: caspase-3 (#9662), cleaved caspase-3 (Asp175) (#9661), Myosin Light Chain 2 (MLC2) (#3672), phospho-MLC2 (Serl9) (#3675), LC3 A/B (#4108), p-(S)-CDKs Substrate (#9477) were obtained from Cell Signaling Technology. Antibodies against GAPDH (#MAB374) were purchased from Millipore. Horseradish peroxidase-conjugated goat anti-mouse or anti-rabbit (Southern Biotechnology) antibodies were then incubated during 1 h and revealed with the SuperSignal West Pico® reagent (Thermo Fisher Scientific) or the ECL™ Prime Western Blotting Detection System (GE Healthcare) using an ImageQuant LAS 4000 software-assisted imager (GE Healthcare).

Statistical Analyses

Each experiment has been repeated at least three times, yielding comparable results. Unless otherwise indicated, figures illustrate quantitative data from one representative experiment (means±SEM, n=3). Data were analyzed by means of Prism v. 5.03 (GraphPad Software, La Jolla, Calif., USA). Statistical significance was assessed by two-tailed Student's t tests. In all experiments, p values <0.05 were considered as statistically significant.

II. Results

Cell Death Profiling Analysis Using Multispectral Imaging Flow-Cytometry Allows the Simultaneous Detection of Non-Cell Autonomous and Cell Autonomous Death Modalities.

The ability of cells to die through NCA processes led us to reconsider from a conceptual point of view our methodological approach to consider cell death processes. Indeed, the choice of the morphological and/or biochemical parameters to be considered as well as the technological approach to be used to detect cell death predefines in advance the results to be expected and does not allow or very rarely to identify new lethal processes such as cellular cannibalism or entosis. The field of radiotherapy is also facing this problem. Indeed, it has been revealed in separate studies that irradiation can trigger many lethal processes such as apoptosis, autophagic cell death, necrosis or mitotic death^(35, 36). It has recently been shown in separate studies that irradiation of the same cell type with the same doses could trigger apoptosis³⁷, but also mitotic death³⁸. In previous studies it was revealed that the onset of apoptosis and mitotic death observed very rapidly following irradiation do not correlate with clonogenic survival observed in the longer term³⁵. These studies highlighted the existence of unknown lethal processes involved in the elimination of irradiated cells. Moreover, the increasing number of publications revealing the influence of cellular cannibalism and entosis in the control of tumor growth and in the elimination of metastatic cells urges one to follow the onset of this process of NCAD.

Considering the diversity of lethal stimuli that can potentially initiate both non-cell autonomous and cell autonomous cell death modalities and the complexity of signaling pathways (involving (or not) caspases, cathepsins or granzymes) that control both processes, it was decided to simultaneously detect non-cell autonomous and cell autonomous death modalities elicited by IR. To determine whether after lethal insults a cellular population may undergo simultaneously direct or/and by-stander-cell killing that may be executed in a cell-autonomous or non-cell autonomous manner, a cell death profiling analysis was designed based on the co-culture of HCT116 cells that have been labeled with 5-chloromethylfluorescein diacetate (CMFDA, green) fluorescent vital probe and treated by ionizing radiations (γ-rays) with isogenic HCT116 cells that have been labeled with 5-(and-6)-(((4-chloromethyl)benzoyl)amino) tetramethylrhodamine (CMTMR, red) fluorescent vital probe. After 24 hours of co-culture, treated CMFDA⁺ cells, untreated CMTMR⁺ cells and the total (CMFDA⁺ cells and CMTMR⁺ cells) cell population were analyzed for phosphatidyl serine (PS) exposure, loss of plasma membrane integrity and DNA content to simultaneously detect cell death induction of both treated cells and (untreated) neighboring cells. To characterize molecular mechanisms involved in the execution of detected cell death modalities, co-cultures were performed in presence cell death modulators (such as ROCK1 inhibitor (Y27632), pan-caspase inhibitor (ZVAD-fmk), caspase-1 inhibitor (YVAD-fmk), necrostatin (NEC1), bafylomycine A1 (BafA1) and Roscovitine (Rosco)) that are respectively known to inhibit cell engulfment (a process that initiates entosis¹⁶, emperiptosis¹⁷ and cellular cannibalism¹⁶), proteolytic cleavage of caspase-3 or caspase-7 (which contributes to the execution of apoptosis³⁹, mitotic death^(38, 40) or emperiposis¹⁷) or of caspase-1 (which is required for pyroptosis⁴¹), the activation of the pro-necroptotic kinase RIP1 kinase (RIPK1) which contributes to necroptosis⁴², the fusion between autophagosomes and lysosomes impairing thus the maturation of autophagic vacuoles during autophagy and autophagy-associated cell death⁴³) and finally, the cyclin-dependent kinase 1 (Cdk1)-Cyclin B activity and the progression through mitosis which is required for mitosis associated deaths such mitotic death^(40, 44). The simultaneous detection of the PS exposure, loss of plasma membrane integrity, DNA content of cellular partners combined with pharmacological inhibition of cell death modulators allowed us to detect during co-cultures through the use of multispectral imaging flow-cytometry the execution of at least 9 cell death modalities (including apoptosis, mitotic death, pyroptosis, autophagic cell death, necrosis, necroptosis, entosis, emperitosis and cellular cannibalism) on targeted cells and on neighboring cells (FIG. 1, A-B), thus discriminating non cell-autonomous deaths from cell autonomous deaths and direct cell killings from bystander lethal effects. This methodology allowed one to define the cell death profiling elicited by IR.

Ionizing Radiation-Elicited Cell Death Profiling Highlights the Induction of Cell Death on Both Irradiated and Non-Irradiated Cancer Cells.

Despite the intensive biological and pharmaceutical research implemented to better characterize cellular and biochemical processes associated with anticancer treatments, lethal mechanisms responsible for the therapeutic effects of radiotherapy, which is one of the most frequent anticancer treatment used in clinic, are still unknown. Lethal processes (such as apoptosis and mitotic catastrophe) that have been detected in response to ionizing radiation were not directly implicated in treatment efficiency³⁵, suggesting that additional cell death modalities that are still unknown may contribute to therapeutic effects of radiotherapy. In this context was determined the cell death profiling of irradiated cancer cells. According to the above described methodology, CMFDA-labeled cells were irradiated or not with 4 grays, mixed after 24 hours together at a 1:1 ratio with CMTMR-labeled cells, and cultured for 24 hours in presence of each indicated inhibitors (Supplementary FIGS. 1A-1E). Then, PS exposure, the membrane integrity and DNA content of each cellular partner were respectively determined using AnnexinV-BV786, DRAQ7 and Hoechst 33342 stainings. Despite no significant increase of apoptotic and necrotic cell deaths (as revealed by the analysis of AnnexinV⁺DRAQ7⁻ and DRAQ7⁺ cells) was observed on neighboring cell population (CMTMR⁺ cells) (FIGS. 2A, 2B and 2D) and on untreated control cell population (FIGS. 2A, 2D and 2E), a significant increase of these both types of death on total cell population (as revealed by considering CMFDA⁺ and CMTMR⁺ cell population) (FIGS. 2A-2C) and on irradiated cell population (CMFDA⁺ cells) (FIGS. 2B and 2E) was detected after 24-hours of co-culture, demonstrating that the present methodology allows to detect cell death modalities of both non irradiated and irradiated cells. It was also observed that the pan-caspase inhibitor Z-VAD-fmk and pharmacological cyclin-dependent kinase inhibitor roscovitine (Rosco) inhibited the exposure of PS on the outer plasma membrane of irradiated CMFDA⁺ cells (FIG. 2E), confirming as previously published^(45, 46) that irradiated CMFDA⁺ cells require both caspase activation and progression through mitosis to die. In addition, the impairment of autophagic flux with bafilomycin A1 (BafA1) increased the frequency of dying cells (AnnexinV⁺DRAQ7⁻ and DRAQ7⁺ cells) in the total cell population (CMFDA⁺ and CMTMR⁺ cells) (FIG. 2C), in non-irradiated CMTMR⁺ cells (FIG. 2D) and in irradiated CMFDA⁺ cells (FIG. 2E), thus revealing that autophagy is a survival cellular mechanism elicited by ionizing radiation that contributes to rescue both non-irradiated and irradiated cells from death. In addition, the simultaneous analysis of the progression of treated and untreated cells through their cell cycles showed that cell death inductions are associated with the escapement of irradiated CMFDA⁺ cells from G1 arrest and led to their accumulations in S and G2/M phases (FIGS. 2F, 2G and 2J). No alteration of cell cycle is detected on total or CMTMR⁺ cell populations, underlining that the cell cycle alterations are only detected on irradiated cells (FIGS. 2F, 2G and 2I). These results, which were also confirmed by classical flow-cytometry analysis (Supplementary FIGS. 2A-2B), demonstrated that after ionizing radiation, both irradiated and non-irradiated cancer cells undergo caspase-1 dependent cell death. Altogether, these results highlighted the ability anticancer agents to simultaneously eliminate cancer cells through direct cell killing and bystander effects.

Ionizing Radiation-Elicited Cell Death Profiling Also Reveals the Induction of Non-Cell-Autonomous Death Modalities.

In parallel, in the same co-culture was determined the ability of irradiated CMFDA⁺ cells to engulf or to invade neighboring cells, two cellular processes required for the induction cellular cannibalism-associated cell deaths (such as cellular cannibalism, emperitosis or phagoptosis) or cell-in-cell invasion-elicited cell deaths (such as entosis). Multispectral imaging flow-cytometry analysis revealed that gamma-irradiated CMFDA⁺ cells triggered the engulfment of neighboring cells (as revealed by the internalization of “target” CMTMR⁺ cells by gamma-irradiated CMFDA⁺ cells (FIGS. 3A and 3B)). This process that was not affected by the pan-caspase inhibitor Z-VAD-fmk is repressed by the inhibitor of ROCK1 (Y27632) (FIG. 3B), thus revealing that the detected cell-in-cell internalization is distinct from phagocytic uptake of apoptotic cells and requires ROCK1 activity to occur. Cannibalistic activity of gamma-irradiated cells was also confirmed by confocal microscopy (FIG. 3D-3F). Interestingly, cell death profiling analysis also allowed to distinguish live cell engulfment from the phagocytosis of apoptotic CMFDA⁺ cells by lived CMTMR⁺ cells that is consecutive to the induction of apoptosis by the treatment with bafylomycin A1 (FIG. 3B). Then, the cell fates of engulfed CMTMR⁺ cells and irradiated engulfing CMFDA⁺ cells were evaluated. It was observed that almost all engulfed CMTMR⁺ cells exhibited signs of cellular degradation (as revealed by the DNA content loss of internalized cells detected with multispectral imaging flow-cytometry (FIG. 3A) and confocal microscopy (FIGS. 3D and 3E)). This process is significantly reduced in presence of the pan-caspase inhibitor Z-VAD-fmk and the caspase-1 inhibitor YVAD-fmk, revealing that IR-mediated death of engulfed cells requires caspases to occur and may be executed through caspase-1 dependent apoptosis, that is also known as pyroptosis. In addition, it was also revealed that 90% of cannibal cells did not expose PS or exhibit loss of the integrity of their plasma membrane (Supplementary FIG. 2C) underlining that after IR-mediated cell engulfment, the internalized cells are precipitated to death without modulating the viability of cannibal cells. Altogether, these results demonstrated that ionizing radiation simultaneously eliminates cancer cells through combined effects of direct cell killing, bystander lethal effect and cellular cannibalism-associated cell death. These results highlight the urgent need to simultaneously measure the induction of non-cell autonomous and cell autonomous death subroutines during lethal processes.

Chemical Library Screening Leads to the Identification of IR-Mediated Cellular Cannibalism Enhancers.

Then, the screening of a library of chemical compounds was developed in order to identify compounds able to induce IR-mediated cellular cannibalism. Thus, HCT116 cells that have been treated with a radiation dose of 8 Gray were stained either with orange CMTMR cell tracker or green CMFDA cell tracker and cultivated in presence of 10 μM of chemical compounds. After 24 hours of culture, cells have been stained with nuclear dye (5 μg/ml of Hoechst 33342 during 1 h at 37° C.) and analyzed using the FlowSight® Imaging Flow Cytometer for cellular cannibalism. Each of these compounds were classified according to their Z-score⁴⁷ and identified respectively 13 and 11 candidate compounds (FIGS. 4A, 4B, 4F and 4G). Then, the identified compounds were validated by combining flow cytometry approaches (in order to eliminate cytotoxic compounds by simultaneously monitoring the depolarization of the internal mitochondrial membrane and the plasma membrane permeability of the treated cells) with confocal microscopy approaches (to confirm the modulation of IR-induced cellular cannibalism by candidate compounds) (FIGS. 4C-E and 4H-J). After the completion of three independent experiments, chemical compounds with no effect (such as Fenbendazol or Carbimazole) or exhibiting high cytotoxicity (such as RN-1-183) have been eliminated. Finally, 16 chemical compounds that are able to enhance the capacity of IR to trigger cellular cannibalism were identified (FIGS. 4E and 4J, Tables 1&2).

The Combination of IRCCE with IR Induces Efficient Antitumor Immunity.

Considering that immunogenic cell death (ICD) inducers were identified (such as Digoxin, Digitoxin, Lanatoside C or Doxorubicin hydrochloride)^(3, 4, 48-51)) as IRCCE, the ability of these compounds to induce an antitumor immunity after radiotherapy was evaluated. First, a preclinical approaches was developed to study the immunological effects of IRCCE on two mouse models of carcinoma (colon CT26 carcinoma and fibrosarcoma MCA205). Initially, the ability of the combination of IRCCE+IR to trigger a specific anti-tumor immune response was appreciated using immunocompetent mice through anti-tumor vaccination assays. According to previously published studies⁵², the injection of cancer cells succumbing to an immunogenic cell death (ICD) into immunocompetent mice must elicit a protective immune response that is specific for tumor antigens. Thus, 3×10⁵ MCA205 cells were first treated with 10 μM of SG6163F for 24 hours. Then, treated cells were inoculated subcutaneously in 200 μl PBS into the lower flank of 8-week-old female C57BL/6 mice. One week later, 3×10⁴ untreated control cells were inoculated into the contralateral flank of mice. Tumors were evaluated weekly using a common caliper. Animals bearing tumors that exceeded 20-25% body mass were euthanatized. It was observed that mice treated with IR or SG6163F alone are not able to induce a significant increase of cell death in vitro (FIG. 5A). In fact, they did not exhibit a protective response after the inoculation of untreated cells, revealing that the dose of radiation and the concentration of SG6163F used were not sufficient to stimulate an anticancer immune response (FIG. 5B). These results were consistent with previously published results demonstrating that a protective response is only detected when cancer cells were exposed to cytotoxic anticancer treatment in vitro until 70% of the cells expose phosphatidylserine on the outer leaflet of the plasma membrane⁴⁸. Surprisingly, it was observed that the combined treatment of MCA205 cells with 8 Gy of IR and 10 μM of SG6163F induced a protective response in 3 of 5 mice that have been injected (FIG. 5B). These results revealed for the first time that the combination of IRCCE+IR may elicit an IR-mediated anticancer immune response in absence of a significant increase of death of treated and irradiated cells (FIG. 5A), suggesting that cellular cannibalism or cellular cannibalism-associated signaling pathways may contribute to the induction of tumor immunogenicity. Then, 3×10⁶ CT26 cells were irradiated with 8 Gy in presence of 10 μM of SG6163F (FIGS. 5E and 5F), VP331 (FIGS. 5I and 5J), Minaprine dihydrochloride (FIGS. 5M and 5N) or LOPA87 (FIGS. 5Q and 5R) for 24 hours. Then, cells were inoculated as previously described subcutaneously in 200 μl PBS into the lower flank of 8-week-old female BALB/c mice. One week later, 5×10⁵ untreated control cells were inoculated into the contralateral flank of mice and tumors were evaluated weekly using a common caliper. As previously mentioned, animals bearing tumors that exceeded 20-25% body mass were euthanatized. The percentage of dying cells in each condition was evaluated by determining with DiOC(6)3/IP staining (FIGS. 5E, 5I, 5M and 5Q). Finally, the ability of these compounds to repress the growth of cancer cells that have been injected 7 days after injection of irradiated and treated cancer cells was appreciated. It was observed a significant increase in the frequency of mice showing a protective response after injection of cancer cells that have been treated with IR and chemical compounds (FIGS. 5H, 5L, 5P and 5T).

A second anti-tumor vaccination assay was done on CT26 mouse models of carcinoma as previously described. Briefly, CT26 cells were irradiated with 8 Gy in presence of 10 μM of VP331 (FIG. 6A, 6F, 6K), Minaprine dihydrochloride (FIG. 6B, 6G, 6L), LOPA87 (FIG. 6C, 6H, 6M), SG6163F (FIG. 6D, 6I, 6N), or Azaguanine-8 (8-aza) (FIG. 6E, 6J, 6O) for 24 hours. Then, cells were inoculated as previously described into immunocompetent BALB/c mice. Finally, the ability of these compounds to repress the growth of cancer cells that have been injected 7 days after injection of irradiated and treated cancer cells was appreciated. The previous results were confirmed. Significant increases in the frequency of mice showing a protective response after injection of cancer cells that have been treated with IR and chemical compounds was observed (FIGS. 6P and 6Q). Interestingly, minaprine dihydrochloride (FIGS. 6B, 6G, 6L, 6P and 6Q) and azaguanine-8 (FIGS. 6E, 6J, 6O, 6P and 6Q) alone induce an increase of protective response after injection of cancer cells.

Altogether, these results revealed the ability of chemical compounds identified with the present platform to induce a protective anticancer immune response.

BIBLIOGRAPHIC REFERENCES

-   1 Tobias J S. Clinical practice of radiotherapy. Lancet 1992;     339:159-163. -   2 Apetoh L, Ghiringhelli F, Tesniere A et al. The interaction     between HMGB1 and TLR4 dictates the outcome of anticancer     chemotherapy and radiotherapy. Immunol Rev 2007; 220:47-59. -   3 Apetoh L, Ghiringhelli F, Tesniere A et al. Toll-like receptor     4-dependent contribution of the immune system to anticancer     chemotherapy and radiotherapy. Nature medicine 2007; 13:1050-1059. -   4 Ghiringhelli F, Apetoh L, Tesniere A et al. Activation of the     NLRP3 inflammasome in dendritic cells induces IL-1beta-dependent     adaptive immunity against tumors. Nature medicine 2009;     15:1170-1178. -   5 Michaud M, Martins I, Sukkurwala A Q et al. Autophagy-dependent     anticancer immune responses induced by chemotherapeutic agents in     mice. Science 2011; 334:1573-1577. -   6 Kingsley D P. An interesting case of possible abscopal effect in     malignant melanoma. The British journal of radiology 1975;     48:863-866. -   7 Ohba K, Omagari K, Nakamura T et al. Abscopal regression of     hepatocellular carcinoma after radiotherapy for bone metastasis. Gut     1998; 43:575-577. -   8 Postow M A, Callahan M K, Barker C A et al. Immunologic correlates     of the abscopal effect in a patient with melanoma. The New England     journal of medicine 2012; 366:925-931. -   9 Rees G J, Ross C M. Abscopal regression following radiotherapy for     adenocarcinoma. The British journal of radiology 1983; 56:63-66. -   10 Demaria S, Ng B, Devitt M L et al. Ionizing radiation inhibition     of distant untreated tumors (abscopal effect) is immune mediated.     International journal of radiation oncology, biology, physics 2004;     58:862-870. -   11 Meng Y, Beckett M A, Liang H et al. Blockade of tumor necrosis     factor alpha signaling in tumor-associated macrophages as a     radiosensitizing strategy. Cancer research 2010; 70:1534-1543. -   12 Dewan M Z, Galloway A E, Kawashima N et al. Fractionated but not     single-dose radiotherapy induces an immune-mediated abscopal effect     when combined with anti-CTLA-4 antibody. Clinical cancer research:     an official journal of the American Association for Cancer Research     2009; 15:5379-5388. -   13 Kroemer G, Galluzzi L, Vandenabeele P et al. Classification of     cell death: recommendations of the Nomenclature Committee on Cell     Death 2009. Cell death and differentiation 2009; 16:3-11. -   14 Vanden Berghe T, Vanlangenakker N, Parthoens E et al.     Necroptosis, necrosis and secondary necrosis converge on similar     cellular disintegration features. Cell death and differentiation     2010; 17:922-930. -   15 Aaes T L, Kaczmarek A, Delvaeye T et al. Vaccination with     Necroptotic Cancer Cells Induces Efficient Anti-tumor Immunity. Cell     reports 2016; 15:274-287. -   16 Overholtzer M, Mailleux A A, Mouneimne G et al. A nonapoptotic     cell death process, entosis, that occurs by cell-in-cell invasion.     Cell 2007; 131:966-979. -   17 Wang S, He M F, Chen Y H et al. Rapid reuptake of granzyme B     leads to emperitosis: an apoptotic cell-in-cell death of immune     killer cells inside tumor cells. Cell death & disease 2013; 4:e856. -   18 Brown G C, Neher J J. Eaten alive! Cell death by primary     phagocytosis: ‘phagoptosis’. Trends in biochemical sciences 2012;     37:325-332. -   19 Brown G C, Vilalta A, Fricker M. Phagoptosis—Cell Death By     Phagocytosis—Plays Central Roles in Physiology, Host Defense and     Pathology. Current molecular medicine 2015; 15:842-851. -   20 Sierro F, Tay S S, Warren A et al. Suicidal emperipolesis: a     process leading to cell-in-cell structures, T cell clearance and     immune homeostasis. Current molecular medicine 2015; 15:819-827. -   21 Khandelwal S, van Rooijen N, Saxena R K. Reduced expression of     CD47 during murine red blood cell (RBC) senescence and its role in     RBC clearance from the circulation. Transfusion 2007; 47:1725-1732. -   22 Lagasse E, Weissman I L. bcl-2 inhibits apoptosis of neutrophils     but not their engulfment by macrophages. The Journal of experimental     medicine 1994; 179:1047-1052. -   23 Overholtzer M, Brugge J S. The cell biology of cell-in-cell     structures. Nat Rev Mol Cell Biol 2008; 9:796-809. -   24 Li Y, Sun X, Dey S K. Entosis allows timely elimination of the     luminal epithelial barrier for embryo implantation. Cell reports     2015; 11:358-365. -   25 Benseler V, Warren A, Vo M et al. Hepatocyte entry leads to     degradation of autoreactive CD8 T cells. Proc Natl Acad Sci USA     2011; 108:16735-16740. -   26 Ni C, Huang L, Chen Y et al. Implication of cell-in-cell     structures in the transmission of HIV to epithelial cells. Cell     research 2015; 25:1265-1268. -   27 Ni C, Chen Y, Zeng M et al. In-cell infection: a novel pathway     for Epstein-Barr virus infection mediated by cell-in-cell     structures. Cell research 2015; 25:785-800. -   28 Bartosh T J, Ullah M, Zeitouni S, Beaver J, Prockop D J. Cancer     cells enter dormancy after cannibalizing mesenchymal stem/stromal     cells (MSCs). Proc Natl Acad Sci USA 2016; 113:E6447-E6456. -   29 Lugini L, Matarrese P, Tinari A et al. Cannibalism of live     lymphocytes by human metastatic but not primary melanoma cells.     Cancer research 2006; 66:3629-3638. -   30 Wang S, Guo Z, Xia P et al. Internalization of N K cells into     tumor cells requires ezrin and leads to programmed cell-in-cell     death. Cell research 2009; 19:1350-1362. -   31 He M F, Wang S, Wang Y, Wang X N. Modeling cell-in-cell structure     into its biological significance. Cell death & disease 2013; 4:e630. -   32 Sun Q, Cibas E S, Huang H, Hodgson L, Overholtzer M. Induction of     entosis by epithelial cadherin expression. Cell research 2014;     24:1288-1298. -   33 Cano C E, Sandi M J, Hamidi T et al. Homotypic cell cannibalism,     a cell-death process regulated by the nuclear protein 1, opposes to     metastasis in pancreatic cancer. EMBO molecular medicine 2012;     4:964-979. -   34 Sun Q, Luo T, Ren Y et al. Competition between human cells by     entosis. Cell research 2014; 24:1299-1310. -   35 Abend M. Reasons to reconsider the significance of apoptosis for     cancer therapy. International journal of radiation biology 2003;     79:927-941. -   36 Gudkov A V, Komarova E A. The role of p53 in determining     sensitivity to radiotherapy. Nature reviews Cancer 2003; 3:117-129. -   37 Zhang P, Castedo M, Tao Y et al. Caspase independence of     radio-induced cell death. Oncogene 2006; 25:7758-7770. -   38 Castedo M, Perfettini J L, Roumier T, Andreau K, Medema R,     Kroemer G. Cell death by mitotic catastrophe: a molecular     definition. Oncogene 2004; 23:2825-2837. -   39 Garcia-Calvo M, Peterson E P, Leiting B, Ruel R, Nicholson D W,     Thornberry N A. Inhibition of human caspases by peptide-based and     macromolecular inhibitors. The Journal of biological chemistry 1998;     273:32608-32613. -   40 Castedo M, Perfettini J L, Roumier T et al. The cell cycle     checkpoint kinase Chk2 is a negative regulator of mitotic     catastrophe. Oncogene 2004; 23:4353-4361. -   41 Miao E A, Leaf I A, Treuting P M et al. Caspase-1-induced     pyroptosis is an innate immune effector mechanism against     intracellular bacteria. Nature immunology 2010; 11:1136-1142. -   42 Degterev A, Huang Z, Boyce M et al. Chemical inhibitor of     nonapoptotic cell death with therapeutic potential for ischemic     brain injury. Nature chemical biology 2005; 1:112-119. -   43 Yamamoto A, Tagawa Y, Yoshimori T, Moriyama Y, Masaki R,     Tashiro Y. Bafilomycin A1 prevents maturation of autophagic vacuoles     by inhibiting fusion between autophagosomes and lysosomes in rat     hepatoma cell line, H-4-II-E cells. Cell structure and function     1998; 23:33-42. -   44 Meijer L, Borgne A, Mulner O et al. Biochemical and cellular     effects of roscovitine, a potent and selective inhibitor of the     cyclin-dependent kinases cdc2, cdk2 and cdk5. European journal of     biochemistry 1997; 243:527-536. -   45 Lowe S W, Schmitt E M, Smith S W, Osborne B A, Jacks T. p53 is     required for radiation-induced apoptosis in mouse thymocytes. Nature     1993; 362:847-849. -   46 Vakifahmetoglu H, Olsson M, Zhivotovsky B. Death through a     tragedy: mitotic catastrophe. Cell death and differentiation 2008;     15:1153-1162. -   47 Zhang X D, Yang X C, Chung N et al. Robust statistical methods     for hit selection in RNA interference high-throughput screening     experiments. Pharmacogenomics 2006; 7:299-309. -   48 Menger L, Vacchelli E, Adjemian S et al. Cardiac glycosides exert     anticancer effects by inducing immunogenic cell death. Science     translational medicine 2012; 4:143ra199. -   49 Obeid M, Panaretakis T, Joza N et al. Calreticulin exposure is     required for the immunogenicity of gamma-irradiation and UVC     light-induced apoptosis. Cell death and differentiation 2007;     14:1848-1850. -   50 Obeid M, Tesniere A, Ghiringhelli F et al. Calreticulin exposure     dictates the immunogenicity of cancer cell death. Nature medicine     2007; 13:54-61. -   51 Casares N, Pequignot M O, Tesniere A et al. Caspase-dependent     immunogenicity of doxorubicin-induced tumor cell death. The Journal     of experimental medicine 2005; 202:1691-1701. -   52 Green D R, Ferguson T, Zitvogel L, Kroemer G. Immunogenic and     tolerogenic cell death. Nat Rev Immunol 2009; 9:353-363. 

The invention claimed is:
 1. A method for enhancing radiotherapy-mediated cellular cannibalism in cancer cells, said method comprising contacting said cancer cells with Mebhydroline 1,5-napthalene disulfonate salt, Minaprine dihydrochloride, LOPA87, VP331, RN-1-001, RN-1-026, SG6163F, VP450, VP43, LOPA90, LOPA93, LOPA 94, LOPA 101, LOPA104, LOPA105, LOPA106, SG6144, SG6146, SG6149, pharmaceutically acceptable salts thereof, or combinations thereof.
 2. The method of claim 1, for enhancing radiotherapy-mediated cellular cannibalism in patients suffering from cancer.
 3. The method of claim 1, for enhancing tumor immunogenicity in subjects that will receive or that have received a radiotherapy treatment.
 4. The method of claim 1, for inducing a significant protective anticancer immune response in subjects that will receive or that have received a radiotherapy treatment.
 5. The method of claim 1, for potentiating a radiotherapy treatment in a subject in need thereof.
 6. The method of claim 1, for treating cancer, in conjunction with radiotherapy, in a subject in need thereof.
 7. The method of claim 1, wherein said method comprises contacting said cancer cells with LOPA90, LOPA93, LOPA 94, LOPA 101, LOPA104, LOPA105, LOPA106, SG6144, SG6146 or SG6149.
 8. The method of claim 1, wherein said method comprises contacting said cancer cells with Minaprine dihydrochloride, LOPA87, VP331, or SG6163F.
 9. The method of claim 1, wherein said cancer cells are in a subject or patient suffering from brain cancer, gastric cancer, head-and-neck cancer, pancreatic cancer, non-small cell lung cancer, small cell lung cancer, prostate cancer, colon cancer, non-Hodgkin's lymphoma, sarcoma, testicular cancer, acute non-lymphocytic leukemia or breast cancer.
 10. The method of claim 1, wherein the contacting step comprises administering said compounds to a subject or patient prior to a radiotherapy treatment.
 11. The method of claim 1, wherein the contacting step comprises administering said compounds to a subject or patient 24 hours prior to a radiotherapy treatment.
 12. The method of claim 1, wherein the contacting step comprises administering said compounds to a subject or patient after a radiotherapy treatment.
 13. The method of claim 1, wherein the contacting step comprises administering said compounds to a subject or patient concomitantly to a radiotherapy treatment.
 14. A method for treating cancer in a subject in need thereof, said method comprising the step of administering to said subject an efficient amount of minaprine dihydrochloride, said method further comprising a radiotherapy treatment step.
 15. The method of claim 14, wherein said subject suffers from brain cancer, gastric cancer, head-and-neck cancer, pancreatic cancer, non-small cell lung cancer, small cell lung cancer, prostate cancer, colon cancer, non-Hodgkin's lymphoma, sarcoma, testicular cancer, acute non-lymphocytic leukemia or breast cancer. 